![]() regarding the last part of your answer:"As long as a photon exists, however, it is made of a superposition of different wavelengths, positions, momentums, etc. Very interesting! Thank you, David, for your answers. In addition, its wavefunction (and corresponding "width," or region in which it can be found) spreads out hyperbolically, just like the laser beam! ![]() As long as a photon exists, however, it is made of a superposition of different wavelengths, positions, momentums, etc. This isn't completely intuitive, since any measurement on a single photon will collapse its wavefunction and yield exactly one position, momentum, wavelength, etc. If you dimmed the laser beam down until it was just a single photon, that photon would behave statistically just like the original laser beam. You can see this if you look at the specs of any commercial laser, for example one. If your laser beam were much smaller, it would diverge faster.)Īs for your second question: all laser beams that can possibly be created do contain at least a small range of wavelengths. This is reasonably large, so the beam doesn't diffract very rapidly. (In addition, keep in mind that a typical laser beam is over 1000 times wider than the wavelength of light. That is why you don't see it spreading out unless you measure carefully, or just measure its size far away from the laser. A gaussian-shaped laser beam is one of the only types of light beams that actually spreads out by this minimum amount. ![]() Most beams spread out much faster than Heisenberg requires. ![]() In contrast, if you shone your handheld laser at the moon, it would expand to over 60,000 meters (~40 miles) wide!Īn interesting fact to notice, however, is that the uncertainty principle only fixes the minimum amount a beam can spread out. That's the smallest spot you could make on the moon. By the time it reached the moon, it would "only" be 16 meters across. If you tried to hit the moon with a laser, you'd want to use a BIG beam- 8 meters (24 feet) in radius. In fact, take your laser out to a field at night and look at it on a screen as far away as you can, and the beam will be huge! If you measure the laser beam at varying distances, you will find that its size continually increases at a hyperbolic rate. Light which is confined to a small aperture does indeed spread out in accordance with the uncertainty principle. the shorter the pulse->larger the z-momentum uncertainty?) but a single photon can have multiple frequencies? or a ultra-short laser pulse cannot be made of a single photon but splits spontaneously into multiple photons with different frequencies? First of all, does a photon have just a single frequency or it has multiple frequencies (is made of a superposition of multiple frequencies?)? - Anonymous The range of λ's gives a range of z-momenta for the photons of the beam.that range of wavelengths corresponds to a small range of colors." ()ĭoes this mean that a laser beam contains(is made of? is a superposition of?) a small range of? various wavelengths(colors) from its head till tail? 0r mainly its head and tail contain different wavelengths where the wave must cancel out and disappear but the main middle part contains almost a single wavelength? And, does a very short pulse-like laser packet made of a single photon contain a single frequency or it must contain various frequencies to create a packet? (it cannot have a single frequency? due to uncertainty principle? i.e. 1)A laser beam spreads out if it goes through a narrow gap or hole due to uncertainty principle, correct? but why a laser beam coming out from a "narrow hole" of a laser pointer/emitter seems to stay as a narrow beam and not to spread out? The hole of the emitter (looks quite small though)is large enough to keep the beam straight or the laser emitter/pointer has special mechanisms to prevent spread?Ģ)"Otherwise the component sine waves couldn't cancel outside that position range.
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